1. Field of the Invention
The present invention relates to information processing apparatuses and methods, recording media, and programs. More particularly, the invention relates to an information processing apparatus and method, a recording medium, and a program in which compression-coded video data can be played back without performing complicated bank memory control.
2. Description of the Related Art
As video compression techniques, the Moving Picture Coding Group/Moving Picture Experts Group (MPEG) is widely used. Playback operations performed by decoding stream data coded by an MPEG method include, not only a normal playback operation, but also a fast playback operation or a reverse-direction playback operation.
For example, in MPEG long groups of pictures (GOPs), each GOP including 15 pictures, a fast playback operation can be performed at ×−3 to ×3 (the sign “−” in the speed indicates that the playback operation is performed in the reverse direction, and the same applies to the following description) by omitting bidirectionally predictive-coded (B)-pictures before being input into a decoder (for example, see Japanese Unexamined Patent Application Publication No. 8-98142). Additionally, a table indicating picture information to be displayed is provided for each playback speed so that playback operations can be performed at different speeds of the same number as that of tables.
Another playback technique is disclosed in Japanese Unexamined Patent Application Publication No. 8-56334. In this technique, 10 frames of a compression-coded signal are obtained intermittently at intervals of 5 frames. After demodulating all the 10 frames of the compression-coded signal, they are alternately supplied to two decoders, five frames to each decoder, and they are decoded and then written into a memory. The memory reads every other frame so that a ×2 playback signal can be output.
MPEG streams are best suited to a playback operation in the forward direction. For example, in MPEG long GOPs, the coding order of 15 pictures, i.e., intra-coded (I)-pictures, predictive-coded (P)-pictures, and B-pictures, forming one GOP is I(2), B(0), B(1), P(5), B(3), B(4), P(8), B(6), B(7), P(11), B(9), B(10), P(14), B(12), and B(13) (the numbers in parentheses indicate the order when the GOP pictures are rearranged in the display order from the coding order). P-pictures predict from one preceding I-pictures or P-pictures, and B-pictures predict from one preceding I-pictures or P-pictures and two preceding I-pictures or P-pictures in the coding order. Accordingly, by reserving two banks of a reference image memory, both the P-pictures and B-pictures can be decoded, thereby enhancing the efficient use of the memory.
To play back MPEG streams best suited to a forward-direction playback operation in the reverse direction, the following technique has been proposed in Japanese Unexamined Patent Application Publication No. 10-150635. A plurality of decoders are used for performing decoding processing, and a GOP immediately before a GOP to be decoded is added and the two GOPs are supplied to a decoder. This enables the correct use of reference images of pictures to be played back even in the reverse-direction playback operation.